1. Field of the Invention
The present invention relates to an intake air throttle valve device for controlling the amount of intake air in accordance with the traveling condition of a vehicle.
2. Description of the Related Art
FIG. 7 is a front elevational view of an intake air throttle valve device, and FIG. 8 is a right side view of FIG. 7.
This intake air throttle valve device includes a rotatable throttle shaft 3 extending through a body 1 in which an intake passage 2 is formed, a throttle valve 4 fixedly secured to the throttle shaft 3, a throttle gear 5 fixedly mounted on an end portion of the throttle shaft 3, a motor gear 6 which is in meshing engagement with the throttle gear 5, a motor shaft 7 of a motor 8 having one end thereof fixedly attached to the motor gear 6, and an elastic member 9 which is arranged to surround the throttle shaft 3 for stopping the throttle valve 4 at a prescribed angle of rotation by balance between a force from the throttle gear 5 and an opposing elastic force of the elastic member 9, which acts in a direction oppose to the force from the throttle gear 5.
The elastic member 9 is made of rubber in the form of a segmental shape which is a partially cut-away circle. The elastic member 9 is formed at its opposite ends with a first engagement portion 9a and a second engagement portion 9b, respectively, both extending in a diametral or radial direction. In addition, the first engagement portion 9a is in abutment against a first abutment surface 10a of an arc-shaped and belt-shaped stopper 10 which is formed on and protruded from the body 1. The second engagement portion 9b is in abutment against a second abutment surface 10b of the stopper 10.
Moreover, the first engagement portion 9a of the elastic member 9 is pressed by a first extension 5a extending from a strut or column 5c of the throttle gear 5 in the clockwise direction, so that the elastic member 9 is subjected to compressive deformation in the clockwise direction. Also, the second engagement portion 9b of the elastic member 9 is pressed by a second extension 5b extending from the strut 5c of the throttle gear 5 in the counterclockwise direction, so that the elastic member 9 is subjected to compression deformation in the counterclockwise direction.
In the intake air throttle valve device as constructed above, the amount of opening or opening degree of the throttle valve 4 is proportional to the amount of operation of an accelerator pedal associated therewith, and the throttle valve 4 serves to adjust the amount of intake air passing through the intake passage 2 in consideration of the operating condition of a vehicle such as, for example, wheel slippage or the like due to differences or variations in rotation of the front and rear wheels, thereby controlling the output power of an internal combustion engine installed on the vehicle. Therefore, the opening and closing operation of the throttle valve 4 is performed under the drive of the motor 8 which is operated on the basis of the amount of operation of the accelerator pedal and data of slippage (slip amounts) or the like, instead of using a direct structure such as a link mechanism directly connecting between the accelerator pedal and the throttle valve.
In this intake air throttle valve device, the motor gear 6 is driven to rotate by energizing the motor 8, so that the throttle gear 5, which is in meshing engagement with the motor gear 6, is thereby turned, thus causing the throttle shaft 3 and the throttle valve 4 integral with the throttle gear 5 to rotate, too. At this time, the elastic force from the elastic member 9 acts on the throttle gear 5 in a direction opposite the rotational direction of the throttle gear 5, so that the throttle valve 4 is stopped at a position at which the rotational force of the throttle gear 5 becomes in balance with the elastic force of the elastic member 9.
The rotational angle of the throttle valve 4 is detected by an opening sensor (not shown) so that a rotational angle signal of the opening sensor is sent as an output value to a control circuit (not shown) where it is determined whether the output value has reached a set target value. When the output value has not yet reached the set target value, the current value of the motor 8 is controlled by a signal from the control circuit whereby the torque of the throttle shaft 3 is adjusted to stop the throttle valve 4 at a new rotational angle.
Next, reference will be made to a mechanism through which the elastic force of the elastic member 9 becomes in balance with the rotational force of the throttle gear 5.
For instance, when the throttle valve 4 in the state of FIG. 7 is to be turned in the clockwise or opening direction, the throttle gear 5 is caused to rotate in the clockwise direction by a driving force applied thereto from the motor 8 through the motor gear 6, whereby the first extension 5a pushes the first engagement portion 9a. At this time, since the second engagement portion 9b is in abutment against the second abutment surface 10b of the stopper 10, the elastic member 9 is compressively deformed in accordance with the clockwise rotation of the first engagement portion 9a, whereby the elastic force of the elastic member 9 is increased with the increasing compressive deformation thereof. When the elastic force of the elastic member 9 becomes balanced with the rotational force of the throttle gear 5, the rotation of the throttle valve 4 is stopped. FIG. 9 shows the state at that time.
On the other hand, when the throttle valve 4 is to be rotated in the closing direction from its fully opened state, the amount of electric power supplied to the motor 8 is reduced to decrease the driving force of the motor 8, whereby the elastic force of the compressed elastic member 9 acting in the counterclockwise direction overcomes the clockwise rotational force acting on the throttle gear 5. As a result, the throttle gear 5 is caused to rotate in the counterclockwise direction through the first engagement portion 9a and the first extension 5a. Thus, the elastic member 9 is expanded in accordance with the rotation of the throttle gear, thereby reducing the elastic force of the elastic member 9. When the elastic force of the elastic member 9 becomes balanced with the rotational force of the throttle gear 5, the rotation of the throttle valve 4 is stopped.
Here, note that when the throttle valve 4 is fully closed, the second extension 5b and the second engagement portion 9b are placed in abutment with each other, and the first engagement portion 9a and the first abutment surface 10a are also placed in abutment with each other, so the elastic force of the elastic member 9 acts on the throttle valve 4 in the opening direction.
In addition, when the throttle valve 4 is fully opened, the first extension 5a and the first engagement portion 9a are placed in abutment with each other, and the second engagement portion 9b and the second abutment surface 10b are also placed in abutment with each other, so the elastic force of the elastic member 9 acts on the throttle valve 4 in the closing direction.
In the above-mentioned intake air throttle valve device, at the instant when the elastic force of the elastic member 9 becomes balanced with the rotational force of the throttle gear 5, the rotation of the throttle valve 4 is stopped. Thus, when the motor 8 is not energized, the first engagement portion 9a of the elastic member 9 must be in abutment with the first abutment surface 10a of the stopper 10 and the first extension 5a, and the second engagement portion 9b of the elastic member 9 must be in abutment with the second abutment surface 10b of the stopper 10 and the second extension 5b. 
However, when gaps or clearances are developed between the first and second engagement portions 9a, 9b and the stopper 10 due to dimensional errors or the like in the first and second engagement portions 9a, 9b, the first and second extensions 5a, 5b and the stopper 10, there arises the following problems.
That is, in FIG. 7, when the throttle valve 4 is to be turned in the closing or counterclockwise direction, the throttle gear 5 is caused to rotate in the counterclockwise direction under the action of the driving force from the motor 8 through the motor gear 6, whereby the second extension 5b pushes the second engagement portion 9b. At this time, since there is a gap A between the first engagement portion 9a and the first abutment surface 10a of the stopper 10, the first engagement portion 9a pushes the first extension 5a without pressing the first abutment surface 10a of the stopper 10. As a result, the elastic member 9 is caused to rotate as it is without being subjected to counterclockwise compressive deformation, that is, the throttle gear 5 is turned in a no-load state without receiving the elastic force of the elastic member 9. Consequently, the opening of the throttle valve 4 can not be controlled according to the amount of electric power supplied to the motor 8 in a rotational range of the gap A, as shown by broken lines in FIG. 10, thus adversely influencing the rotational speed control of the internal combustion engine.
The present invention is intended to solve the problem as referred to above, and has for its object to provide an intake air throttle valve device in which even if there would be developed gaps between engagement portions and a stopper due to dimensional errors in the engagement portions, extensions and the stopper, the influence of the gap on the control of the opening of a throttle valve can be reduced.
In order to achieve the above object, the present invention resides in an intake air throttle valve device which includes: a motor; a body having an intake passage formed therein; a throttle shaft extending through the body; a throttle valve fixedly secured to the throttle shaft; a throttle gear fixedly attached to an end portion of the throttle shaft for transmitting a driving force from the motor to the throttle shaft thereby to open or close the throttle valve; and an elastic member or a coiled torsion spring arranged to surround the throttle shaft for stopping the throttle valve at a prescribed angle of rotation by balance between a force from the throttle gear and an opposing elastic force of the elastic member or coiled torsion spring. The elastic member or coiled torsion spring is engaged at one end thereof with an end face of a stopper provided on the body, and at the other end thereof with the throttle gear, so that the elastic force of the elastic member or coiled torsion spring can be changed by the deformation of the elastic member or coiled torsion spring in accordance with the operation of the throttle gear. In an intermediate portion of the elastic member or coiled torsion spring, there is provided a load applying element for causing the elastic means to generate a force to oppose the force of the throttle gear thereby to apply a load to the throttle gear.
With the above arrangement, even in cases where there is a gap between an end of the throttle gear and an adjacent end face of a stopper, the throttle gear is able to receive the elastic force of the elastic member in the entire operating range of the throttle gear. As a result, the opening of a throttle valve can be statically determined by balance between the force from the throttle gear and the elastic force from the elastic member, thus making it possible to prevent the occurrence of a range in which it is impossible to control the opening of the throttle valve in accordance with the amount of electric power supplied to the motor.
The above and other objects, features and advantages of the present invention will become more readily apparent to those skilled in the art from the following detailed description of preferred embodiments of the present invention taken in conjunction with the accompanying drawings.